The fundamental steps of processing color light-sensitive materials generally include a color developing step and a silver removing step (e.g., bleaching step, bleach-fixing step, etc.). Thus, an imagewise exposed silver halide color photographic material undergoes a color developing step, where silver halide is reduced with a color developing agent to produce silver and the oxidized color developing agent in turn reacts with a color former to yield a dye image. Subsequently, the color photographic material undergoes a silver removing-step, where silver produced in the developing step is oxidized with an oxidizing agent (usually called a bleaching agent), and is dissolved away with a silver ion complexing agent, usually called a fixing agent. Therefore, only a dye image is formed in the thus processed photographic material. In addition to the above described two fundamental steps of color development and silver removal, actual development processing involves auxiliary steps for maintaining the photographic and physical quality of the resulting image or for improving the preservability of the image. Some examples of these auxiliary steps include a hardening bath for preventing a light-sensitive layer from being excessively softened during photographic processing, a stopping bath for effectively stopping the developing reaction, an image stabilizing bath for stabilizing the image, and a layer removing bath for removing the backing layer on the support.
The above described silver removal step may be conducted in two basic ways: one way uses two steps individually employing a bleaching bath and a fixing bath; and the other way is more simple and is conducted in one step employing a bleach-fixing bath containing both a bleaching agent and a fixing agent for the purpose of accelerating the processing and elimination of labor.
In recent years, bleach processing using a ferric ion complex salt (for example, aminopolycarboxylic acid ferric ion complex salt, particularly iron (III) ethylenediaminetetraacetate complex salt) as a major bleaching component has mainly been employed in processing color photographic light-sensitive materials in view of the acceleration and simplification of the bleaching provided and the need to prevent environmental pollution.
However, ferric ion complex salts have a comparatively low oxidizing power and, therefore, have generally insufficient bleaching power. A bleaching or bleach-fixing solution containing such a complex salt as a bleaching agent can attain some desirable objects when bleaching or bleach-fixing a low speed silver halide color photographic light-sensitive material containing, for example, a silver chlorobromide emulsion as a major component. However, such a solution provides insufficient desilveration due to insufficient bleaching power or requires a long time to bleach when processing a high speed, spectrally sensitized silver halide color photographic light-sensitive material containing a silver chlorobromoiodide emulsion or a silver iodobromide emulsion as a major component, particularly color reversal light-sensitive materials for photography or color negative light sensitive materials for photography comprising an emulsion containing a larger amount of silver.
In the color light-sensitive materials, sensitizing dyes are generally employed for the purpose of spectral sensitization. In particular, when a silver halide emulsion containing a large amount of silver or tabular grains having a high aspect ratio is employed in order to achieve high sensitivity, a problem occurs in that sensitizing dyes adsorbed on the surfaces of silver halide grains interfere with the bleaching of silver formed during the development step.
Known bleaching agents, other than ferric ion complex salts, include persulfates. Persulfates are usually used in a bleaching solution together with a chloride. However, this type of persulfate-containing bleaching solution has less bleaching ability than ferric ion complex salts, thus requiring a substantially long period of time for bleaching.
As described above, bleaching agents which do not cause environmental pollution or corrode vessels and apparatus usually have only a weak bleaching power. Hence, it is desired to enhance the bleaching power of a bleaching solution or a bleach-fixing solution containing a weak bleaching agent, particularly a ferric ion complex salt or a persulfate.
In order to increase the bleaching power of a bleaching solution or a bleach-fixing solution containing a ferric ion complex salt such as iron (III) ethylene-diaminetetraacetate as a bleaching agent, it has been heretofore proposed to add various bleach accelerating agents to the processing bath.
Examples of such bleach accelerating agents include various mercapto compounds as described, for example, in U.S. Pat. No. 3,893,858, British Patent 1,138,842 and JP-A-53-141623 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), compounds having a disulfide bond as described, for example, in JP-A-53-95630, thiazolidine derivatives as described, for examples, in JP-B-53-9854 (the term "JP-B" as used herein means an "examined Japanese patent publication), isothiourea derivatives as described, for example, in JP-B-53-94927, thiourea derivatives as described, for example, in JP B-45-8506 and JP-B-49-26506, thioamide compounds as described, for example, in JP-A-49-42349, and dithiocarbamates as described, for example, in JP-A-55-26506.
Among these bleach accelerating agents, although some compounds certainly exhibit a bleach accelerating function, their effects are not always sufficient. Further, these compounds are extremely unstable in a processing solution, particularly in a bleach-fixing solution and lose their effects in a short period of time. Therefore, they are not always suitable for practical use.
Other bleach accelerating agents, for example, onium compounds as described, for example, in U.S. Pat. No. 3,748,136, phenylene linking ammonium salts as described, for example, in JP-B-54-12056, and amine compounds as described, for example, in U.S. Patent 4,552,834 are also known. However, these compounds have only weak bleach accelerating effects and they are not always suitable for practical use, although they are stable in a bleaching solution or a bleach-fixing solution.
Moreover, the compounds as described in JP-B-60-24936 do not always show a satisfactory bleach accelerating effect, although they do exhibit a certain degree of bleach accelerating effect. Further, they often form stains in the case of continuous processing.
As described above, many of these bleach accelerating agents do not always show a satisfactory bleach accelerating effect, and some of them lack stability in the processing solution although they exhibit an excellent bleach accelerating effect. Therefore, they provide a processing solution having only a short effective life or which cannot be stored for a long time.
The above-mentioned compounds as described in JP -B-60-24936 show a certain degree of bleach accelerating effect and are capable of being stored for a relatively long period of time. However, such compounds, as noted, still have a problem in that they often form stains on the photographic material thus-processed.